Gas dilution apparatus

ABSTRACT

Gas dilution apparatus for providing a source of a dilute gas containing a pollutant gas component for detection and/or analysis, in which a gas stream containing a pollutant gas is drawn into the apparatus and through first passage means and a trap to a gas scrubbing assembly. A small quantity of the gas stream containing the gaseous pollutant is drawn off from the first passage means by way of a restricted flow passage for admixture with the scrubbed gas from the gas scrubber assembly, with the restricted flow passage including heating means operatively connected thereto to maintain the temperature of the restricted flow passage above the due point of the gas stream.

United States Patent 11 1 Lyshkow [451 Jul 1,1975

[ GAS DILUTION APPARATUS [75] Inventor:

[73] Assignee: Combustion Equipment Associates Inc., New York, NY.

221 Filed: June 13, 1974 21 Appl. No.: 478,881

Related US. Application Data [62] Division of Ser. No. 441,170, Feb. 11,1974, Pat. No.

Norman A. Lyshkow, Chicago, 111.

55/318, 319, 386, 387, 418, 417, 467, 485, 512, 97, 98; 73/19, 28, 421R, 421.5 R, 421.5 A, 422 GC, 422 TC [56] References Cited UNITED STATESPATENTS 3,794,909 Smith .1 55/270 X 5/1974 Austin et a1. 55/270 10/1974Boubel 55/270 X Primary ExaminerFrank W. Lutter Assistant Examiner-DavidL. Lacey [57] ABSTRACT Gas dilution apparatus for providing a source ofa clilute gas containing a pollutant gas component for de' tectionand/or analysis, in which a gas stream containing a pollutant gas isdrawn into the apparatus and through first passage means and a trap to agas scrubbing assembly. A small quantity of the gas stream containingthe gaseous pollutant is drawn off from the first passage means by wayof a restricted flow passage for admixture with the scrubbed gas fromthe gas scrubber assembly, with the restricted flow passage includingheating means operatively connected thereto to maintain the temperatureof the restricted flow passage above the due point of the gas stream.

14 Claims, 5 Drawing Figures GAs DILUTION APPARATUS This is a divisionof application Ser. No. 44l,l70, filed Feb. 11, 1974, now US. Pat. No.3,853,516.

This invention relates to a fluid dilution apparatus, and moreparticularly to a gas dilution apparatus for use in taking gas samplesfrom gas streams containing pollutant gases.

In the sampling of gas streams containing pollutant gases, including SS0 N0 etc., it is sometimes necessary to dilute the gas stream tofacilitate accurate measurements of the pollutant gas content of thestream. This is particularly so where the gas stream contains relativelyhigh concentrations of the pollutant gas, and the high concentration ofpollutant gas tends to obscure sensitive measuring and/or detectionequipment.

One convenient means to dilute the gas stream is to simply admix the gasstream with a diluent gas to reduce the concentration of the pollutantgas to a level within the sensitivity of the measuring and/or detectionequipment being used. However, it is generally undesirable to employambient air as the diluent gas because the ambient air may contain ameasurable concentration of the pollutant gas which would obviouslyintroduce error into the measurements made as to the pollutant gasconcentration. It is difficult to attempt to correct for such errorsince the concentration of the pollutant gas in the ambient air may besubject to significant variation over the period during whichmeasurements are to be made.

It has therefore been necessary, to avoid the disadvantages stemmingfrom the use of ambient air as the diluent gas, employing a source of agas which is inert to the analytical system, such as nitrogen, helium,etc. The use of such inert gases is not only expensive, but requiresthat the equipment include bulky containers for the storage of suchinert diluent gases. Moreover, the use of such inert gases involvescomplex mixing equipment which is difficult to control within the verynarrow limits required for accurate analysis.

Gas sampling equipment of the type described is subject to furtherdisadvantages in that the gas streams which are subjected to analysisoften contain condensible components, such as water vapor and/or solidparticulate matter. It has sometimes been the practice to employcondenser and filtration equipment to remove such components. However,the use of such equipment contributes significantly to the bulk and costof the gas sampling equipment and frequently to the introduction oferror to the analysis.

It is accordingly an object of the present invention to provide fluiddilution apparatus which overcomes the numerous disadvantages describedabove.

It is a more specific object of the invention to provide fluid dilutionapparatus for use in taking gas samples and the like in which thediluent gas is obtained from the gas stream sampled without affectingthe concentration of pollutant gases in the sample.

It is a related object of the present invention to provide fluiddilution apparatus for use in taking samples of fluid streams in whichthe condensible components and/or solid particulate matter can beremoved without the need for costly and complex condensation andfiltration systems.

These and other objects and advantages of the invention will appear morefully hereinafter, and, for purposes of illustration and not oflimitation, an embodiment of the invention is shown in the accompanyingdrawings in which:

FIG. 1 is a side view in elevation of dilution apparatus embodying thefeatures of this invention;

FIG. 2 is a sectional view taken along the lines 2--2 in FIG. 1',

FIG. 3 is a detailed side view in elevation of the apparatus shown inFIGS. 1 and 2;

FIG. 4 is another side view of the apparatus of FlGS. 1 to 3; and

FIG. 5 is a detailed view, partially in section of the needle assemblyof the apparatus of FIGS. 1 to 4.

The concepts of the present invention reside in a compact, portablefluid dilution apparatus which can be used to sample gases from a gasstream containing one or more pollutant gases in which the diluent gasis derived from a portion of the gas stream itself without the need toemploy an exterior source of a diluent gas. In accordance with thepractice of the invention, the apparatus includes means to draw a gassample through the apparatus for purification to form a diluent gas, andmeans to divert a small quantity of the gas sample, prior topurification, through a by-pass circuit for admixture with the diluentgas. The small quantity of the gas sample is diverted at low flow rateswhereby the gas sample diverted does not have sufficient energy toentrain solid particulate matter and/or droplets of condensed liquids,and consequently, such components are separated from the gas sample asthe small portion is diverted.

In this way, the small quantity of the gas sample which contains thepollutant gas is admixed with the inert diluent gas in controlledproportions to provide a diluted gas stream which can be subjected toanalysis and/or monitoring.

Referring now to the drawings for a more detailed de scription of theinvention, there is shown dilution apparatus which embodies the conceptsof the invention. The apparatus includes a body generally designated as10 including a cylindrical portion 12 mounted on a block portion 14. Theblock portion is provided with gas inlet means 16 which is preferablyprovided with a gas sampling member 18 in the form of a long, hollowtube communicating with the gas inlet means. The gas sampling tube 18can be fixed to the gas inlet means 16 by way of a threaded member 20which is adapted to threadedly engage corresponding threads 22 of thegas inlet means 16.

As is best illustrated in FIG. 3 of the drawing, the block portion 14 ofthe housing 10 defines first passage means 24 which communicate with thegas inlet means 16 and trap means 26 adapted to collect solidparticulate matter and/or condensed liquids. For this purpose, the firstpassage means can be provided with a tubular member 28 whichcommunicates with the first passage means 24 and extends into the trapmeans 26. The trap means 26 is preferably a transparent container toenable a visual inspection of the contents thereof to determine when thetrap means is full, and can be removably mounted on the block portion 14of the housing 10 by means of threads 30 adapted to engage acorresponding threaded portion 32 of the block portion 14. In this way,the trap means 26 can simply be removed and emptied when full.

As shown in FIG. 3, the block portion 14 also defines second passagemeans 34 which also communicates with the trap means 26 and whichterminates in a generally conically shaped chamber 36. Second passagemeans 34 preferably includes a hollow tubular member 38 which extendsinto the trap means 26 as shown in FIGS. 3 and 4; however, the tubularmember 38 preferably does not extend as far into the trap means 26 asdoes the tubular member 28.

As shown in FIG. 3, the cylindrical portion 12 of the body also includesa gas scrubbing assembly referred to generally as 40. The purpose of thegas scrubbing assembly is to remove all components, including thepollutant gas component of the gas sample to provide a stream of adiluent gas which is inert to the analysis and/or detection system withwhich the diluter may be used. Consequently, the nature of the scrubbingassembly depends to some extent on the pollutant gas contained in thegas sample.

In the embodiment illustrated in FIG. 3, the scrubber assembly isintended for use with and/or SO systems and includes two or moreseparate zones. The scrubber assembly illustrated includes threeseparate scrubbing zones, each of which is separated from the adjacentzones by foraminous supports 42. The first zone 44 is adapted to containa material which will remove water vapor from the gas stream, and ispositioned directly above the conical chamber 36. In the preferred formof the invention, the first zone 44 is adapted to contain silica which,as is known to those skilled in the art, is capable of absorbing watervapor until it becomes wetted. Thus, the silica operates to dischargecondensed water vapor as it becomes wet, and the water vapor thusdischarged is collected in the conical chamber 36 for passage throughthe passage 34 to the trap 26.

The second zone as illustrated in FIG. 3 is formed of an adsorbentmaterial which is capable of adsorbing pollutant gases contained in thegas stream and any other reactive components contained in the gasstream. In the preferred practice of the invention, the adsorbent forremoving such reactive materials is a material which is capable ofadsorbing and/or reacting with acidic components of the gas stream, suchas CO, S0 S0 etc. For example, use can be made of well known adsorbents,such as sodium hydrate-asbestos adsorbent which is marketed by Arthur H.Thomas Co. under the trademark Ascarite. This material, of course,serves to remove CO, S0 S0 and like components from the gas stream.

The scrubber assembly is also preferably provided with a zone containingactivated carbon as an adsorbent. This zone is shown as 48 in FIG. 3. Aswill be appreciated by those skilled in the art, the activated carbonserves to remove any other contaminants which may be present in the gasstream. Depending on the composition of the gas stream, the third zoneof activated carbon may be dispensed with if desired.

The cylindrical portion 12 of the housing I0 also defines a scrubbed gaspassage which communicates with the scrubbing assembly and terminates ina chamber 52, also defined by the cylindrical portion 12. The scrubbedgas passage also is provided with discharge means 54 adapted to beconnected to a source of reduced pressure to draw gases through theapparatus, as more fully described hereinafter, for discharge. Discharge means 54 is thus adapted to be connected with analysis ordetection apparatus or to a vacuum pump whose discharge is connected tosuch apparatus.

Positioned in the chamber 52 is needle means 56 which is in the form ofa hollow needle, one end of which projects into the scrubbed gas passage50 past the discharge means 54, as is most clearly illustrated in FIG. 5of the drawing. As shown in this figure, the discharge means 54 includesdischarge passage means 58 bridging the scrubbed gas passage 50 and thedischarge 54 to provide communication between the scrubbed gas passage50 and the discharge 54.

As is also shown in FIG. 5 of the drawing, the needle 56 is mounted on ahub 60 which is threadably engaged at 62 with the block portion 14 ofthe housing I0. The needle 56 is a double needle and, as describedabove, one end thereof 64 extends into scrubbed gas passage 50. Theother end 66 of the needle extends into the first passage means 24 topermit a small, controlled amount of the gas stream entering theapparatus and containing one or more pollutant gases to pass from thefirst passage means 24 through the needle 56 and into the scrubbed gaspassage 50 where it is mixed with the scrubbed gas; the diluted mixtureresulting is conse quently drawn out through the discharge means 54 foranalysis and/or detection of the gaseous pollutant con tained therein.

The cross-sectional area of the needle 56 is of course quite small orrestricted as compared to the cross sectional area of the first passagemeans 24, and consequently, the bulk of the gases entering the apparatusflows through the first passage means 24. The small amount of the gasstream which does pass through the needle has low kinetic energy whichinsures that particulate matter and/or droplets of liquids which havecondensed in the apparatus are not carried into the needle but arecarried along with the bulk of the gases flowing through the firstpassage means 24 and into the trap 26 in which they settle out bygravity. Thus, the low kinetic energy of the gases passing through theneedle effects a separation of solid and liquid components without theneed to employ filters or the like.

In the embodiment shown in the drawings, no variable valving means inthe needle are shown. However, it will be appreciated by those skilledin the art that adjustable valve means may be provided in the needle ifdesired. It is sometimes preferable to provide valve means 68 in thescrubbed gas passage to control the How of scrubbed gases therethrough.

In the most preferred practice of the invention, the hub 62 on which theneedle is mounted is formed of metal and includes heating meansassociated therewith to insure that the plug and consequently the needleare maintained at a temperature above the dew point of the gases passingthrough the needle. In this way, condensation in the needle isprevented. The heating means is designated 70 in FIGS. 4 and 5 of thedrawing in which it is illustrated schematically. The heating means 70includes a heater 72 which may be a glow plug or the like, and anindicator light 76 to indicate when the heater is operating. Alsoincluded is a thermostat 74 to prevent overheating of the needle. As isbest seen in FIG. 5, heat from the glow plug 72 is transmitted to thehub 62 by conduction through a suitable heat conductor 78 bridging theglow plug and the hub.

Power for the heating means 70 can be supplied from any convenientsource. In the ilustrated embodiment, power is supplied by batteries(not illustrated) contained in a suitable receptacle 79 mounted on thehousing 10. The receptacle can conveniently be a flashlight barrelthreadably engaged with the block portion 14 of the housing 10. Wiringhas not been illustrated for the sake of simplicity of the drawings.

in the preferred practice of the invention, the hub 60 is preferablyprovided with a layer of insulation 80 to minimize heat lossestherefrom. For this purpose it is frequently convenient to wrap or coatthe hub 60 with Teflon or like material which is non-heatconductive.

In the use of the apparatus of this invention, the gas sampling member18 is inserted into a gas stream, such as the gas stream flowing througha stack 82 as shown in FIGS. 1 and 2. A vacuum is applied to thedischarge means 54 to draw gases from the gas stream through the gassampling member 18 and through the inlet means 16 into the first passagemeans. The bulk of the gas stream containing the gaseous pollutanttherein passes through the first passage means to the tube means 28 andinto the trap 26 to deposit particulate matter and any liquid dropletswhich may have condensed from the gas stream. The gas in the trap 26 isdrawn thereafter through the tube means 38 and through the secondpassage means 34 and the scrubber 40 for the removal of pollutant gasesand/or any other reactive components in the gas stream. Consequently,the gas which is drawn out of the scrubber assembly through the scrubbedgas passage means 50 is inert with respect to the detection and/oranalysis system with which the apparatus of this invention is to beused.

As the gas stream is drawn through the apparatus, a small quantity ofthe gas stream containing the gaseous pollutants is withdrawn from thefirst passage means 24 through the needle 56 into the scrubbed gaspassage means 50. As indicated above, the needle provides a restrictedflow passage in which the gases flowing therethrough have a very lowkinetic energy and therefore are incapable of entraining solidparticulate matter and/or droplets of condensed liquids. As long as thenegative pressure applied to the discharge means 54 remains constant,the volume of flow through the needle remains in a constant proportionto the volume of flow through the scrubbed gas passage means 50 tothereby provide a constant rate of dilution which does not vary withtime.

The gas stream containing the pollutant gases therein which passesthrough needle 56 is admixed with the scrubbed gas drawn through thescrubbed gas passage means 50 for discharge through discharge means 54for detection and/or analysis.

The apparatus of this invention provides a simple and efficientdetection means in which there is no need to employ complex filtrationand/or condensation apparatus. The device of this invention iscompletely portable, compact and lightweight since it is unnecessary tosupply an inert diluent gas from any outside source as the inert gas isgenerated in the apparatus itself.

It will be understood that various changes in the details ofconstruction, operation and use may be made without departing from thespirit of the invention, especially as defined in the following claims.

I claim:

I. Apparatus for diluting fluids comprising a body, gas inlet means forreceiving a gas stream containing a pollutant gas, first passage meansin the body communicating with the gas inlet means, trap means mountedon the body and communicating with the first passage means to receivethe gas stream flowing therethrough, gas scrubbing means adapted toremove the pollutant gas from the gas stream flowing therethrough, viasecond passage means which communicate with the trap means and thescrubbing means, gas discharge means adapted to be connected to a zoneof reduced pressure, scrubbed gas passage means communicating with thescrubbing means and the discharge means and restricted flow passagemeans extending into the scrubbed gas passage means and extending intothe first passage means whereby reduced pressure applied at thedischarge means draws the gas stream through the inlet means and throughthe first passage means to provide flow of the bulk of the gas streamthrough the first passage means to the trap means and then through thegas scrubbing means for removal of pollutant gas therefrom and to forman inert diluent gas and to provide flow of a small amount of the gasstream containing pollutant gas through the restricted flow passagemeans to permit admixture of the small amount of the gas streamcontaining pollutant gas, with the restricted flow passage meansincluding heating means operatively connected thereto to maintain thetemperature of the restricted flow passage means above the due point ofthe gas stream.

2. Apparatus as defined in claim 1 wherein the inlet means includes gassampling means adapted to be inserted into the gas stream.

3. Apparatus as defined in claim 1 wherein the trap means is removablymounted on said body and is formed of a transparent material to permitvisual inspection of the contents thereof.

4. Apparatus as defined in claim 1 wherein the trap means communicateswith the first passage means through first tube means and the trap meanscommunicates with the second passage means through second tube means,with the first tube means projecting into the trap means farther thanthe second tube means.

5. Apparatus as defined in claim 1 wherein the gas scrubbing meansincludes one or more zones containing a material capable of removingpollutant gas from the gas stream.

6. Apparatus as defined in claim 1 wherein the gas scrubbing meansincludes three zones, with one zone containing means adapted to removewater from the gas stream, with the second zone containing means adaptedto remove pollutant gas from the gas stream, and with the third zonecontaining means adapted to remove any remaining impurities in the gasstream.

7. Apparatus as defined in claim 1 wherein the gas scrubbing means ispositioned in a cavity in the body, with the base of the gas scrubbingmeans being positioned about a conical chamber adapted to receive liquidfrom the gas scrubbing means for return to the trap means through thesecond passage means.

8. Apparatus as defined in claim 1 which includes valve means in thescrubbed gas passage means to control the flow of gases therethrough.

9. Apparatus as defined in claim 1 wherein the restricted flow passagemeans is a hollow needle having a small cross-sectional area whereby thesmall amount of gas flowing therethrough has a low kinetic energy topermit solid and liquid components to pass to the trap means.

10. Apparatus as defined in claim 9 wherein the scrubbed gas passagemeans terminates in a chamber, with the needle being positioned in thechamber extending into the scrubbed gas passage means.

the gas stream.

13. Apparatus as defined in claim 12 wherein the heating means includesthermostat means to prevent overheating of the needle.

14. Apparatus as defined in claim 12 wherein the hub includes insulationto prevent heat loss therefrom.

1. APPARATUS FOR DILUTING FLUIDS COMPRISING A BODY, GAS INLET MEANS FORRECEIVING A GAS STREAM CONTAINING A POLLUTANT GAS, FIRST PASSAGE MEANSIN THE BODY COMMUNICATING WITH THE GAS INLET MEANS, TRAP MEANS MOUNTEDON THE BODY AND COMMUNICATING WITH THE FIRST PASSAGE MEANS TO RECEIVETHE GAS STREAM FLOWING THERETHROUGH, GAS SCRUBBING MEANS ADAPTED TOREMOVE THE POLLUTANT GAS FROM THE GAS STREAM FLOWING THERETHROUGH, VIASECOND PASSAGE MEANS WHICH COMMUNICATE WITH THE TRAP MEANS AND THESCRUBBING MEANS, GAS DISCHARGE MEANS ADAPTED TO BE CONNECTED TO A ZONEOF REDUCED PRESSURE, SCRUBBED GAS PASSAGE MEANS COMMUNICATING WITH THESCRUBBING MEANS AND THE DISCHARGE MEANS AND RESTRICTED FLOW PASSAGEMEANS EXTENDING INTO THE SCRUBBED GAS PASSAGE MEANS AND EXTENDING INTOTHE FIRST PASSAGE MEANS WHEREBY REDUCED PRESSURE APPLIED AT THEDISCHARGE MEANS DRAWS THE GAS STREAM THROUGH THE INLET MEANS AND THROUGHTHE FIRST PASSAGE MEANS TO PROVIDE FLOW OF THE BULK OF THE GAS STREAMTHROUGH THE FIRST PASSAGE MEANS TO THE TRAP MEANS AND THEN THROUGH THEGAS SCRUBBING MEANS FOR REMOVAL OF POLLUTANT GAS THEREFROM AND TO FORMAN INERT DILUENT GAS AND TO PROVIDE FLOW OF A SMALL AMOUNT OF THE GASSTREAM CONTAINING POLLUTANT GAS THROUGH THE RESTRICTED FLOW PASSAGEMEANS TO PERMIT ADMIXTURE OF THE SMALL AMOUNT OF THE GAS STREAMCONTAINING POLLUTANT GAS, WITH THE RESTRICTED FLOW PASSAGE MEANSINCLUDING HEATING MEANS OPERATIVELY CONNECTED THERETO MAINTAIN THETEMPERATURE OF THE RESTRICTED FLOW PASSAGE MEANS ABOVE THE DUE POINT OFTHE GAS STREAM.
 2. Apparatus as defined in claim 1 wherein the inletmeans includes gas sampling means adapted to be inserted into the gasstream.
 3. Apparatus as defined in claim 1 wherein the trap means isremovably mounted on said body and is formed of a transparent materialto permit visual inspection of the contents thereof.
 4. AppaRatus asdefined in claim 1 wherein the trap means communicates with the firstpassage means through first tube means and the trap means communicateswith the second passage means through second tube means, with the firsttube means projecting into the trap means farther than the second tubemeans.
 5. Apparatus as defined in claim 1 wherein the gas scrubbingmeans includes one or more zones containing a material capable ofremoving pollutant gas from the gas stream.
 6. Apparatus as defined inclaim 1 wherein the gas scrubbing means includes three zones, with onezone containing means adapted to remove water from the gas stream, withthe second zone containing means adapted to remove pollutant gas fromthe gas stream, and with the third zone containing means adapted toremove any remaining impurities in the gas stream.
 7. Apparatus asdefined in claim 1 wherein the gas scrubbing means is positioned in acavity in the body, with the base of the gas scrubbing means beingpositioned about a conical chamber adapted to receive liquid from thegas scrubbing means for return to the trap means through the secondpassage means.
 8. Apparatus as defined in claim 1 which includes valvemeans in the scrubbed gas passage means to control the flow of gasestherethrough.
 9. Apparatus as defined in claim 1 wherein the restrictedflow passage means is a hollow needle having a small cross-sectionalarea whereby the small amount of gas flowing therethrough has a lowkinetic energy to permit solid and liquid components to pass to the trapmeans.
 10. Apparatus as defined in claim 9 wherein the scrubbed gaspassage means terminates in a chamber, with the needle being positionedin the chamber extending into the scrubbed gas passage means. 11.Apparatus as defined in claim 10 wherein the needle extends into thescrubbed gas passage means beyond the discharge means.
 12. Apparatus asdefined in claim 9 wherein the needle is mounted in a hub in the bodyand the heating means is operatively connected to the hub to maintainthe temperature of the needle above the due point of the gas stream. 13.Apparatus as defined in claim 12 wherein the heating means includesthermostat means to prevent overheating of the needle.
 14. Apparatus asdefined in claim 12 wherein the hub includes insulation to prevent heatloss therefrom.